Hydropneumatic locking cushion for power presses



l v. GEORGEFF 2,584,339

HYDROPNEUMATIC LOCKING CUSHION FOR POWER PRESSES Feb. 5, 1952 GII@ f Y 0 limi:

1NVENTOR. 57 VHS/1 GEORGE/:F

5 Sheets-Sheet l Flled Aprll 6 1949 Arme/EY Feb. 5, 1952 v. GEORGEFF 2,584,339

HYDROPNEUMATIO LOOKING CUSHION FOR POWER PRESSES Filed April 6. 1949 3 Sheets-Sheet 2 se Jo s: m r Y 'Q 1| f y F15' E IN VEN TOR.

VHS/L EOEGEFF Arrow/EY Feb. 5, 1952 v. GEORGEFF 2,584,339

HYDROPNEUMATIC LOCKING CUSHION FOR POWER PRESSES Filed April 6, 1949 5 Sheets-Sheet 3 hatented Feb. 5, 1952 HYDROIANEUMATIC LOCKING CUSHION FOR POWER PRESSES Vasil Georgefl, Chicago, Ill., assignor to Danly Machine Specialties, Inc., Chicago, Ill., a corporation of Illinois Application April 6, 1949, Serial No. 85,744

Claims.

My invention relates to hydropneumatic locking cushions for power presses, and more particularly for double action power presses.

In a double action press, the metal to be worked is fed to the press and is first held in position between the dies by a blank holder. The press then moves to do its work while the blank is being held. After the work is finished, the blank holder moves away, followed by a more rapid action of the die holding ram. Die pins are used to push the work out of the die, in case .that the formed metal is provided with a-reventrant portion. These die pins act against a die cushion or pressure pad. The arrangement is such that the pressurey pad, which returns the die pins to their original .position and at the same time moves the work out of the die, must be delayed until such time as the blank holder and upper die is moved clear of the work. This is usually accomplished by a locking arrangement, which holds the pressure pad from acting to return the die pins until the cycle of operations has brought the blank holder in the upper ram clear of the work. The resistance furnished by the pressure pad or cushion may be either pneumatic or hydraulic, or both. For some types of work a pneumatic cushion is most suitable, and for other types of work, where greater resistances are encountered during a shorter stroke, a hydraulic cushion is most suitable.

One object of my invention .is to provide a exible hydropneumatic cushion in which the same cylinder which cushions the die acts as a locking cylinder.

Another object of my invention is to provide a hydropneumatic locking cushion which may be employed as a simple pneumatic cushion or a hydropneumatic cushion with either locking or non-locking action, as may be desired.

Another object of my invention is to provide a flexible hydropneumatic locking cushion em- 'part vof the instant specication and which are blank holder I0 of the press.

to be read in conjunction therewith, and in which like reference numerals are used to indicate like parts in the various views:

Figure 1 is a sectional elevation through a hydropneumatic locking cushion showing one embodiment of my invention with the blank holder and the ram at the lowest position of their travel just after the completion of the working stroke, in which my invention is adjusted as a simple pneumatic locking cushion.

Figure 2 is a fragmentary view, similar to Figure 1, of the upper portion of my cushion, showing the position of the ram and the blank holder with the cushion in locked position.

Figure 3 is a view similar to Figure l, showing the position of parts of a hydropneumatic cushion after the locking action has been released.

In general, my invention contemplates the provision of a pneumatic pressure pad, in which a piston is adapted to compress air within a cylinder, to provide for a pneumatic cushion. The air piston is connected by a piston rod to a second piston which is adapted to move fluid. The arrangement is such that the resistance-to fluid motion creates a hydraulic resistance and acts as the hydraulic cushion. The motion of the hydraulic piston is adapted to draw liquid from a reservoir to the space above the hydraulic piston within the hydraulic cylinder past a check valve. The imprisonment of this liquid serves to lock the entiresystem, that is, both the pneumatic piston and the hydraulic piston. Timed means are provided for bleeding the liquid above the hydraulic piston back into the reservoir to release the locking action.

By removing the resistance between the bottom of the hydraulic piston and the reservoir,

the hydraulic cushion is automatically eliminated and the hydraulic piston simply acts as a lock for the pneumatic cushion. By 'providing resistance to flow to the liquid below the hydraulic piston, I have a structure which becomes at once both a hydraulic and a pneumatic cushion. By releasing the constraint to the liquid above the hydraulic piston, I have been able to transform my assembly into a simple cushion with no locking features.

More particularly referring now to the drawings:

The bolster l of the press, which may be of any appropriate design, supports a die 6 adapted to cooperate with an upper die 3 attached to the An inner die l2 cooperates with -a punch die I4 attached to the press ram I6, as is well known in the art. The

3 'clank holder l5 is .reciprocated in timed relation with the ram I6, such that the blank holder will contact the Work rst, followed by the press ram. On the up stroke the press ram moves away first, while the blank holder dwells and is then followed by the blank holder moving away. The position of the .parts during Vthe up `stroke ofthe blank holderlanid'the -ram is'shown in vFigure 2. The die i2 acts against die pins I8 which are cushioned by a die cushion, the pressure pad 2li-of which is shown in the drawing.asian-external piston around a cylinder 22. The downward motion of the piston 2t compresses the air beneath it within the cylinder 22. cylinder-serves the additional function of 4'aetingas :la reservoir for a liquid 24. The piston 2U is connected by a piston rod 26 to a hydraulicpistonlfludgd within a hydraulic cylinder 30. As the piston 20 moves downwardly, the hydraulic piston 28 will likewise move downwardly through the same distane-e. The cylinder 2 2- L communicates with the Ycylinder -30 through al-ducti. 'This'.ductlis controlled by a check valve-$4, rpermittinglliquid to filow through-itfiromlthecylinderl22 tothe cylinder- 30v only onthe 'down stroke vof thehydraulic `piston 28. Y'l-t-'will'be 'observedlthat--as fast as liquid lis withdrawnff-rom reservoir 22 --tooccupy vvthe Aspace `Vabove the hydraulic `piston 128, liquid isf replaced-liront below? the piston 281through duct l2 back-#into the-reservoir, thus maintaining the leffec-tivelevelI of liquidi-within theireservoir. The vVc-:onipr-ession"of:theairbetween the upper surfface. of=-t he1liquidllevel andfthe 'piston 20 within the cylinderzwilliact as apneumaticresistance for-'the pressure pad-i215, when the die pins i8 move -i-t downwardly :under the action of the punch-die 1M. The piston im., therefore, in confjunction .1w-ith theicylinde'r 22T-facts as Aa pneumatic cushion. 'YA/locking valve housing 44 is .provided wfithalcy-linder- 46 E11i-which I-position fa pis-ton 48. fllhepisjtonfcarriesahousing'55, into which-the Vvalve stem-Mofa valve54is lodged. Aspringi normally-maintains the valve in -seatedposi-tion, when ithe'- piston 548 is moved to Y.the flef-t- :under itl-ie :act-ion Aof air' introduced y.pressure urging the pistoril-ZEIV upwardly also urges .the .piston 7.8 upwardly. The check valve 34 prevents the liquid from fowing-fthroug-h Vduct e2, and this :pressure vis thus 'communicated through duct .66 into the space `$8 within the locking 4valve -housing 44. `This pressure assists kthe springfBBAinfholding thelvalve 54 onits seat.

'The pressure also acts'upon the piston 'l0 -formed lon the-housing .50- and tends to move the housing .to the Yright-'against the y'action of the pistonf'. `When the cylinder 46 vented this hydraulic pressure'will move the piston to the right until 'the right hand .end ofmember -l contacts the -valve unseating f'button 12 `secured lto the end v of the valve stem 52.. When this occurs, fluid is Y adapted to be transferred/through'duct 56 past the valve 54 which is now in open position,gas shown in FigureY 3, through duct 3B past check valve 38 into thearea belowthe hydraulic-piston 23, permitting the hydraulic piston to move up.- Vwardly under the influencev'offthe vpneumatic sie pressure` behind 'the pneumatic piston-2li.A :This

upward motionofj'the piston 2l]I moves-fthe 'die 40 and the duct'42.

have movedfto-fpositioncleariof the work. The

construction so far described is that of a simple .pneumatic locking cushion. By closing valve 5l .governing.the-airsupply to the cylinder 46, I

'mayconvert vrnystructure into a simple pneumatic cushion. With the air supply in communication withthe'lcylinder 46, We have a pneumatic locking cushion.

Theopening--lis adapted to be closed by a plungerl is carried by a piston 'i8 positioned withinv a cylinder 80. A four-way valve 82icontrols the supply of air from a source under pressure through a pipe 84 into the cylinder te Vto .the left; ,off piston-1 @or .through pipe ,St to the right of. piston '1:85` depending-.upon the position of the four-way ivalve e112. `:When compressed yair is on onesiderioithegpiston `the other side of 'the `piston is vented :by the four-Way valve through pipe! 83. Wherlaair pressureis impressed .to the leftofjpiston'lii't willmove `to the. rightto the position shown :in Figure 3. When the piston 2% and the hydraulicpiston .22 `zmoveidownlwardly under'theinfluence-.of the .force exerted by the die pins l-Bunder the action of the-punch die 4, the liquid beneath .the hydraulic piston 2 mustovercome, theqforcejexerted yby the piston 'i8 before the liquid canlescape'throughthe port VSince the area of vthe hydraulic plunger 16 ismllch smaller thanthatof the air piston 118-a comparatively-'small'amount of air pressure `will exert .'substantially high hydraulic pressure. :A lsimple adjustment. of the air Apressure supplied through .pipe 84 will accuratelyV control the 'hydraulic pressure to be exerted by the hydraulic cushion. With the lplunger '16 normally closing the v port "ed of the hydraulic cylinder -3` 'the .parts .now act as a combined .pneumatic and hydraulic cushion. The locking action `remains the same vand .the

Vpneumatic cushion :servies tofurge the hydraulic piston to, its. upward position. as described above. Thereleasingaction, howeverfwhen In r:cushion operates asfa .-pneumatic-.hydraulic .cushion is vsomewhat different. :It :is complicated -tlie factthat the 'area .below *piston 128 is greater .than'the areaiabove Ithislpistonby thelcross-sectional area of the piston rod 26. lWhen-the valve Sillis opened by 4'veritingthe cylinderild to the atmosphere through pipe -62-l through the action of carni'llytheair pressure below piston :2S will move both'piston 2li' and connected piston 2S upwardly. Y'llrie liquid 'displaced'by the Vupper portion of piston ZBfis smaller in volume than the areajswept by-'the vlower side of the piston 23.

42 `throiiefh the inow openedv port de 'to supply 'the additional' volume'ofliquid" representing the differential in piston area above and below the piston 28. As soon as the piston 28 is moved to its upper position, air is again admitted behind the piston .18 and the plunger 16 again closes the port 40 so that the assembly may act as a hydropneumatic cushion.

It will be readily observed that when the piston 'I8 is moved to the left, that is, in the position shown in Figure 1, and the cylinder 44 is vented to the atmosphere, that is. when both port 40 is opened and valve 54 is 01T its seat the device is a simple pneumatic cushion. y When plunger 16 is operative and valve 54 is off its seat, my assembly acts as a hydropneumatic cushion. When port 40 is open and air pressure -is behind piston 48 my assembly acts as a pneumatic locking cushion. When both the plunger 16 and the valve 54 are operative my assembly is connected to act as a hydropneumatic locking cushion.

The pipe 25 is normally connected to an air surge, the pressure of which determines the pneumatic pressure in the pneumatic system. In event it is not desired to employ die pins, as is sometimes the case with certain dies, piston 48 is positioned to the right by venting the cylinder 44 and piston 18 is moved to the left by applying air pressure through pipe 86 and the air in cylinder 22 is vented through bleeding the pressure by means of pipe 25 and its associated surge tank (not shown). When the parts are in this position all cushion effect is eliminated without any structural changes.

A drain pipe 23 is provided for removing oil or adding oil to the cylinder 22 as desired. The liquid may be drained from thecylinder 30 by removing the valve 31. This valve is also adapted to control the rate at which the piston 26 travels upwardly when the valve 54 is opened. If passage 36 were unobstructed, the piston 2!) would travel upwardly at a speed which would be too great. The end 4I oi the valve 31 is adapted to obstruct the passage 36 to provide a resistance to fluid ilow and thus provide a time interval during which the piston 20 may move upwardly under the influence of air entrapped in cylinder 22. y

It is believed that the operation of my hydropneumatic locking cushion will be clear from the foregoing description.

It will be seen that I have accomplished the objects of my invention. I have provided a flexible hydropneumatic cushion in which the same cylinder which cushions the die acts as a locking cylinder. I have provided a hydropneumatic locking cushion which may be employed as a simple pneumatic cushion or a hydropneumatic cushion with either locking or non-locking action, as may be desired. My hydropneumatic locking cushion employs no auxiliary equipment. It is a self contained unit and is cheaper to construct and easier to maintain than those of the prior art. I may condition my hydropneumatic cushion with facility to act as a simple pneumatic cushion, a simple hydropneumatic cushion, a pneumatic locking cushion -or a hydropneumatic locking cushion, as may be desired.

It will be understood that certain features and sub-combinations are of utility and may be ern- K ployed without reference to other features and sub-combinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims without departing from the spirit of my invention. It is, therefore. to be understood that my invention is not to be limited to the specific details shown and described.

Having thus described my invention, what I claim is:

1. A die cushion for power presses including in combination a first cylinder, a second cylinder, a piston coacting with the first cylinder, a piston in the second cylinder, means connecting said pistons in tandem, the rst of the cylinders containing a quantity of hydraulic fluid below the piston partially filling the cylinder, the other of said cylinders containing hydraulic fluid positioned both above and below the piston, communication means between the rst cylinder below its piston and the second cylinder above its piston, a check valve positioned to permit the flow of hydraulic iiuid from the first cylinder to the second cylinder through said communicating means, a second communication means between the second cylinder below its piston and the rst cylinder, intra-communication means between the upper portion of the second cylinder above its piston and the lower portion of the second cylinder below its piston,I and controlling means for said intra-communicating means.

2. A die cushion for power presses including in combination a first cylinder, a piston coacting with the rst cylinder, said ,rst cylinder containing a quantity of hydraulic fluid partially filling the cylinder and positioned below the piston, a second cylinder, a second piston in the second cylinder, means for connecting the first and second pistons in tandem, said second cylinder containing hydraulic fluid positioned above and below the second piston, communication means between the first cylinder below its piston and the second cylinder above its piston, a check valve positioned to permit the ow of hydraulic huid from the first cylinder to the second cylinder through said communicating means, a second communicating means providing communication between the second hydraulic cylinder below its piston and the first hydraulic cylinder below its piston, means for controlling the flow of hydraulic fluid through said second communicating means, means for varying the action of said controlling means, means providing intra-communication between lthe top of the second cylinder above its piston and the bottom of the second cylinder below its piston and means for controlling the intra-communicating means.

3. A die cushion as in claim 2 in which said controlling means for the intra-communicating means comprises a valve in the intra-communicating means and means for controlling the operation of the valve.

4. A die cushion as in claim 2 in which said controlling means for the intra-communicating means comprises a valve in the intra-communieating means and timed means for controlling the operation of the valve.

5. A die cushion as in claim 2 in which said means for controlling the intra-communicating means comprises a valve in the intra-communicating means, means for controlling the operation of the valve, and a check valve permitting the flow of fluid from above the second piston to below the second piston upon the opening of the first Valve.

6. A die cushion as in claim 2 in which means for controlling the flow of hydraulic fluid through said second communicating means comprises a valve, and an elastic means for placing a. predetermined pressure upon said valve.

7. A die cushion as in claim 2 in which means for controumgfehe new; u:1lnycl-raulre4mm'..thmugh said second communicating means comprises la cylindrical forice, asplunger normallyfseated in said cylindrical orice to close the orifice| endian elastic means for holding mire;` plunger-Ain thev cylindrical orifice.

close said orice, '.an' air'cylnder, apistonwithin the ,air cylinder, means. forconnectingathelpiston -to theplunger-and meanalfor vintroducingcomf Vpressed air -v-nnder laepredeterminedzpressure `loe- -means for controlling :the-intra-communicating means comprisesfar-valvegianan' cylinderaepiston Within lthe airzcylinder, -a hydraulic -icylinder, -a f `piston in the hydraulic-cylinder, v means connecting theair pistonandthehydraulic pistonin tandem, saidV valve.: being adapted@ y beeseatedfby hydraulic fpressure, ifsaid...hydrau1ic -pressure l`biaszing .the tandem iconnected l= pist;ons to :moves-the v:valve from its seat, means forv counter-.acting the hydraulic pressure` kloy air pressure 'introduced nto the cylinder behndfthe iairipi'ston :andftimed means for controllin'gzthe lapplication.*and vent- A-ing of air.

10. A die cushion as in claim 2` includingL means :formintroducing hydraulic fluid into the fustcyl- @finderY below its-piston', .and controlled means -for *venting air from the Irst 4cylinderabove Ithelevel lime f-this A4patent:

Number- .Name Date 1,936,410 :Scholz Nov,21.1933 :2,426,155 Rode `Aug. 19,51947 

